Remember how satisfying coloring books were when you were a kid? This is better, I promise.
Maybe it's my bizarre obsession, as of late, with insanely candy colored floral chintzes getting to me, but I literally "colored in" an old scrap of Schumacher toile using Sennelier's Tinfix fabric paints (just Google for internet retailers). Use a paintbrush— it goes on just like water color— and although the site says it's only for silk and wool, don't listen to them. The dyes are more vibrant on those fabrics, but sometimes, you don't want to need sunglasses to look at your pillows. (Or alternately, drapes. Holy god, I just had a thought...how amazing would giant, billowing drapes of water-colored toile be?!) The toile I used was cotton.